Conventionally, for example, JP 2008-19819 A and the like disclose that in an engine using LPG as a fuel, a vaporizer including a regulator vaporizes a liquid phase LPG fuel stored in a tank into a gas phase fuel by using heat of an engine cooling water, and introduces the high-pressure gas phase fuel into a pressure regulating chamber via a pressure regulating mechanism using a pressure regulating valve opening and closing with a predetermined pressure to allow an injector to supply the gas phase fuel regulated to the predetermined pressure to the engine.
FIG. 1 shows an example of a vaporizer 1 as disclosed in the above-mentioned publication. Here, an LPG fuel passage 4 through which a high-pressure liquid phase LPG fuel stored in a tank (not shown) passes is disposed along an engine cooling water passage 3 formed in a body 2 and is connected to a pressure regulating chamber 6 via a pressure regulating valve 5 attached to the LPG fuel passage 4, the pressure regulating valve 5 is constituted by a valve body 8 which closely contacts with and shuts a valve seat 7 provided on an opening portion to the LPG fuel passage 4 of the pressure regulating chamber 6, one end of a valve lever 12 is connected to a central part of a diaphragm 11 having a compression coil spring 10 partitioning the pressure regulating chamber 6 and a back pressure chamber 9, and the other end of the valve lever 12 is shaft-supported on the valve body 8 by a shaft pin 13, thereby configuring a lever type pressure regulating chamber.
In the conventional vaporizer 1, if a pressure on a downstream side is decreased by delivering the gas phase LPG fuel in the pressure regulating chamber 6 according to the driving of the engine, the diaphragm 11 is displaced to the pressure regulating chamber 6 side to operate the valve lever 12 so that the valve body 8 is lifted to open a valve, thereby introducing the high-pressure gas phase LPG fuel into the pressure regulating chamber 6 and increasing an internal pressure to a predetermined fuel pressure, and a micro opening of the pressure regulating valve 5 is adjusted to reduce the pressure in the pressure regulating chamber 6 to a required pressure and the injector (not shown) supplies the pressure regulated fuel gas to the engine, under a balance between the diaphragm 11 applied with the pressure of the high-pressure LPG fuel vaporized in the LPG fuel passage 4 and the compression coil spring 10 opposite thereto by the engine cooling water 15 flowing through the engine cooling water passage 3 formed in the body 2 and heated by the driving of the engine.
However, if malfunction, damage, or the like related to the pressure regulating mechanism, such as the pressure regulating valve 5, the valve seat 7, the diaphragm 11, and the valve lever 12 occurs, the normal function of the pressure regulating valve becomes impaired. In particular, impurities that adversely affect rubber parts are contained in a large amount in an LPG fuel depending on a production area, and there is a possibility that a rubber portion of the pressure regulating valve 5 in the vaporizer 1 is damaged and thus leading to breakage.
As described above, if the pressure regulating valve 5 fails to close due to a defect of the pressure regulating mechanism as a component of the vaporizer 1, the high-pressure gas phase fuel is supplied to the pressure regulating chamber 6 even after the engine is stopped, and the pressure of the gas phase fuel in the pressure regulating chamber 6 is likely to be abnormally increased. For this reason, the pressure regulating chamber 6 is normally provided with a safety valve 14 constituted by a relief valve. For example, as disclosed in JP 7-23624 Y, a fuel pressure monitoring system of a vaporizer using “safety module” guided to a safe place such as a closed cross-sectional space of a vehicle body by operating a safety valve has been adopted.
In this specification, the “safety module” is referred to as a device for realizing a control of “operating a machine only when safety can be confirmed” in a control system related to safety, and specifically, is referred to as a device for receiving a signal from an “input unit” such as an emergency stop switch or a safety switch to determine whether it is safe or not, and transmitting the signal to an “output unit” such as a contactor based on the determination result.